1. Field of the Invention
The disclosure relates to a control system for a battery and, more particularly, to a technique for correcting an output of a current sensor that detects a charge and discharge current of a battery.
2. Description of Related Art
Japanese Patent Application Publication No. 2005-37286 (JP 2005-37286 A) describes a technique for, in a vehicle including an electrical load, a battery that stores electric power to be supplied to the electrical load, and a current sensor that detects a charge and discharge current of the battery, calculating a learned value of an offset error of the current sensor based on an output of the current sensor just before a stop of a vehicle system and then correcting the output of the current sensor by using the learned value of the offset error.
However, in the case where the vehicle system is started up in an extremely low temperature environment in which the outside air temperature is extremely low, if the output of the current sensor is corrected by using the learned value of the offset error as in the case of JP 2005-37286 A, there is a concern that correction accuracy decreases.
That is, the offset error of the current sensor generally changes in response to the temperature of the current sensor. The temperature of the current sensor mainly depends on the outside air temperature at startup of the vehicle system, and gradually converges (saturates) to a steady temperature after the startup. Therefore, when the vehicle system has been started up after being left to stand in an extremely low temperature environment, the temperature of the current sensor just after the startup is considerably lower than the steady temperature, and accordingly it is assumed that the offset error just after the startup also considerably deviates from the learned value of the offset error (offset error just before a stop of the current sensor). Therefore, in the case where the vehicle system has been started up after being left to stand in an extremely low temperature environment, if the output of the current sensor is corrected by using the learned value of the offset error (the offset error of the current sensor just before a stop of the vehicle system), it is assumed that the output of the current sensor is not accurately corrected.